Definition February 2024 - Web


DEALING WITH HEAT IS COMPLICATED, though not impossible . BUT SPLITTING THE LED AND THE COOLING SYSTEM was our biggest challenge ”

apparently identical colours, as seen by a human, might be created using different mixes of different primaries – and seen differently by a camera. “Any light can reach a given xy point, but the spectrum will be so different – that’s why I was against it,” de Montgrand reflects. Still, the convenience of using two numbers to specify any colour outweighed the odd mismatch. “Gaffer is king here. They like xy because it’s two numbers, and they can count on us to develop a high-quality light engine to make sure the xy is as good as it can be. The two-digit language is the bread and butter of that.” Convenient as full-colour-mixing lights are, as de Montgrand highlights, there is an engineering compromise. Most scenes aren’t lit with brightly coloured light; and a light which can output bright colours may be worse at white light than a dedicated white-only design. The past two years of Rosco DMG’s work have been concerned with developing something to address that question – and it’s taken a while. The company has been quiet on new products while tackling this, but the pre- launch took place at Cine Gear, with final units expected in February. DMG’s Lion is a 1kW LED with a big 330mm fresnel lens and one entirely new feature: a hot- swappable LED module. “It’s for two key reasons,” de Montgrand says. “Firstly, the fastest- evolving element of a light is the LED emitter, and we try to build long-lasting, sustainable products. Secondly, when you’re making white light with colours, you’re missing out on efficiency.” Lion will launch with full colour mixing and high- output, white-emitting modules, though the high-output module retains enough emitters to facilitate colour temperature and green-magenta adjustment. “The

high-output module has twice the output of the Mix module,” de Montgrand explains. “Sometimes, with a fixture this size, it’s also there for you to fight with the elements and the sunshine, if you want a true, 5K-tungsten-like output.” Putting that feature in a power- dense light, de Montgrand confirms, didn’t come easily. “Dealing with heat is complicated, though not impossible,” he says. “But splitting the LED, which generates the heat, and the cooling system was our biggest challenge. Usually, when you interface a heat- generating component on a heat sink, you can never separate them because you compromise the thermal combination of the two. We solved that problem by using a liquid cooling system adopted not just by us, but by a lot of manufacturers. There’s so far you can go passive, then you go active with fans – but that makes noise if you add too many. So, we went the liquid route.” The result, as de Montgrand puts it, is a requirement to “do a mechanical, hydraulic and electrical interface in one movement. You have a little handle, twist it upwards a quarter-turn and it will release the light engine from the system. The swap time is five seconds. You can do it in the back of the truck or on the C stand next to the talent.” The sheer pace of emitter development hints at more than just full colour mixing or white; we have already had hints of a UV-emitting module for special effects. In the end, satisfying curmudgeonly cinematographers that tungsten and HMI light sources have been properly replaced is perhaps as much a matter of artistic interpretation as technology. Still, recognising there remain mountains to conquer, and the efforts being made to conquer them, beckons an interesting future.

Convenience LED lights have occasionally been criticised for their weight, which tends – at the very least – to be more like an HMI than the tungsten-halogen lamps they largely replaced. The Lion weighs 30kg, which de Montgrand accepts is a lot for a 1kW light, though not necessarily unreasonable in comparison to the 5kW light it might replace, as well as comparing favourably with lights of a similar – or even slightly higher – power level. The choice to concentrate the mass in one device was, de Montgrand reports, largely driven by the desires of gaffers. Calibration LED lighting is not the only technology which has the potential to drift off colour as it ages, although it is probably the first to offer at least the potential for recalibration to match different units. This is something Rosco DMG considers part of a warranty service, as de Montgrand explains. “If you own a DMG Dash Octa Case with eight of them in there, and one of them is off, you can send it to me to fix it within three years for free. After six years, I’ll probably charge you £50 for the operation. We read all of the photometric data for each of our channels – and save that photometric data in the module.”



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